Automatic center punch



sep111,1945. L A SWEET .2,384,707

AUTOMATIC CENTERv PUNCH Filed Sept. 29, 1942 1 8 7 4 faja-f? 2j 6 24 l a j! 1498 5 2017)@ 23 \22 Y1 5 J0 Je f JNVENTOR.

Patented Sept. 11, 1945 UNITE D .STATES PAT EN T O I 2,384,707v

AUTOMATIC CENTER PUNCH Laurence Sweet, Huntington Park, Calif.

Application September 29, 1942, Serial No. 460,165

v2. Claims.

`My invention relates'to improvements in automatic center punches and the like. An object of this invention is to make acenter punch which can be made to strikea blow ,uponthepunch by merely pressing down on the outside casing of the mechanism. This .enables the opera-tor to place center punch marks with greater accuracy and rapidity, and with much less effort than by any other method.

A further object 0f my invention is to provide means to vary the force of .the blow upon the head of the center Vpunch so as to make punch marks of varying depth and diameter, ,thus .providingfor the starting of drills of different sizes. A still further object of my invention isto make the punch and striking mechanism that theparts are very simple and sturdy, and will give long and satisfactory service.

Further objects and advantages of my invention 'will appear as the specication proceeds.

The preferred form of my invention is illus.- trated in theaccompanying drawing in which: Fig. 1 is a side View of the complete tool. Fig. 2 is an enlarged longitudinal section of the tool showing the parts in released position.

Fig. 3 is an enlarged flongitudinalsectionfof ythe. tool showing the parts raised and the springs compressed about to the point at which-the harnmer is tipped to strike the blow on the punch.

Fig. 4 is an enlarged cross-section of the `tool showing the position of the parts :just `after the hammer has struck the blow onthepunch.

In practicing this invention, I lprovide Ya construction by means of .which ,a punch or punch plunger I is automatically actuated, that is to say, if the point of the vpunch plunger is held against a surface and pressure isexerted on the case or body I of the holder, the punchwill :move

relatively outwardly, vor --toward the rear of the body. This relative movement forces back a hammer 2| with which is associated a spring 24, the movement being imparted from the butt end of the punch to the hammer through the agency of a tumbler I4. When the tumbler has moved rearwardly suciently to store up considerable energy in the spring, the tumbler is tripped, that is to say, it is moved automatically into position, which will release the hammer 2l and permit the hammer to be moved suddenly forward by its spring 24. In this forward movement of the hammer, a part of the hammer impinges upon the rear end of the tumbler so that the tumbler acts to impart the blow from the hammer to the butt end I3 of the punch. The face of the butt end of thepunch and the adjacent end face of the tumbler, havea correlated form which .will enable these faces to cooperate -to holdtheitumblernormally in a position that will enable it toengage the forward face of the hammerand impart :the withdrawing movement of `the lhammer to :the hammer. The tumbler .is preferably of spindle form, andthe constructionorformcf ,the said correlated faces is such-.that they will `normally hold the tumbler in the position in which the relative backward movementof the punch will push back the .hammer and energize itsspring. The construction includes means tofbe described hereinafter, operating at. ,a certain point .in .the backward movement .of the punch and tumbler, to trip the tumbler, that. is to say. to shift it laterally into a position in which it will no 'longer be capable of pushing back the hammer. Then the blow is struckl and imparted through the rtumone with a projecting point, the other with a` nat face to engage this point. This projecting point, in the present instance, is obtained by forming a conical faceor cone end I3 on thebutt end of the punch, which rests against aflat face formed at-the forward end or head of the tumbler I4. However, it should be understood that it is merely necessary to form these faces so that if pressure is exerted from the butt end ofthe punch to the tumbler, there is nothing inherent in the form or contact of these faces that would tendlto keep the tumbler in a position that would permit l the hammer to be moved forward by-its spring.

In other words, these contacting faces are formed so that they will tend to hold the tumbleriin a position toimpart movement from the punch v.to the hammer and push it back when .the punch is pressed forcibly againstthe surface. The tumbler is preferably of spindle form with a head at its end adjacent to the cone I3. The body I5 of this tumbler is preferably of smaller diameter than the head I 4, andthe rear end of the tumbler is preferably formed into a stem I6 of substantially uniform diameter. Between the stem and the body I5 0f the tumbler, I prefer to form an inclined or tapered neck I1 which operates as a cam when this neck engages the edge of the shoulder or constriction 3 which forms the reduced opening 1. When this occurs the tumbler will be tripped, that is to say, it will be moved into a position in which its longitudinal axis is brought substantially into alignment with the axis of the hammer. This will bring the stem into alignment with the bore 23 of the hammer, and release the hammer to strike its blow upon the tumbler. Although I do not consider it essential to the performance rof this operation to employ a spring to maintain the tumbler in its active position, that is to say, a position in which it can exert thrust upon the hammer to withdraw the hammer, I do prefer to employ a small coil spring 20 disposed around the tumbler, and I prefer to employ an angle washer I8 having an inclined face against which this spring seats. By reason of this inclined face the spring exerts its force to hold the tumbler in its active position (see Fig. 2). This small spring 20 prevents any possibility of the end of the stem I from accidentally getting into alignment with the bore 23 of the hammer when the punch Ill is being shoved against the face that is to be punchmarked. 'I'he forward face of this washer I8 is disposed in a plane substantially at right angles to the axis of the hole through the washer, and this face seats against the shoulder I9 on the rear side of the enlarged head of the tumbler I4. The rear end of the spring 20 thrusts against annular shoulder 3 within the body I of the tool.

The punch holder guide 8 has a small bore fitting to the diameter of the punch plunger I, and a counterbore 9 to receive its butt end II so that the punch plunger I is retained in thepunch holder 8 by the shoulder I2. The punch holder 8 is screwed into the sleeve I at the internally threaded portion 4. l

In the bore of the body I is placed the hammer 2l which in normal position rests against the shoulder 3 of the body I. The ha-mmer 2l is shouldered at 22 and a blind bore is formed centrally therein, said bore 23 being of slightly larger diameter than the stem yII: oi the spring which i's compressed by the backward movement of the hammer. In the present instance, against the shoulder 22 of the hammer 2I rests compression spring 24, the opposite end of this spring 24 being retained by a cap 25 which is preferably adjustably threaded onto the sleeve or body I at the externally threaded portion 6 of the sleeve I.

To operate the tool the punch point should be placed against the surface that is to be punch marked,-with the sleeve or body I and cap 25 grasped firmly in one hand. A quick inward or downward pressure exerted 'on the tool then forces the punch plunger` I0 and tumbler I4 relatively upwards 'against the spring 2B. This presses the tipof stem I6 of the tumbler I4 yagainst the bottom of the hammer 2 I, and the instem IE off center and against the forward end of the hammer 2 I. This moves the hammer 2l relatively back and against the pressure of the spring 24 until the point is reached where the taper Il on the tumbler I4 strikes the camming shoulder or constriction 3. As the diameter of the neck I5 is a sliding t in the opening 'I of the shoulder 3, this will align the stem I6 of the tumbler I4 centrally with the hole 23 of the hammer 2l and release the hammer 2I so that the spring 24 forces the hammer 2| quickly downward orl forward over the stem I6 so that the bottom of the bore 23 strikes a sharp blow upon the upper end of stem IGVof the tumbler I4, said blow being transmitted to the punch I0 through the tumbler Iii and driving the point of the punch IG into the material being marked. The force of the blow struck by hammer 2I may be regulated by ad- `iusting the cap 25 0f the body I by means of the threads 6 so as to increase 0r decrease the compression force for spring 24. Release of the downward pressure on body I allows all parts tn return to the normal position as shown in Fig. 2 in readiness for the next blovv.y

Many other embodiments of the invention may be resorted to without departing from the spirit of the invention.

What I claim is tl 1. An automatic centerpunch comprising: a tubular housing lhaving'a constriction intermediate its ends forming a camming element; a punch plunger slidable in said housing at one side of said constriction and protruding from said housing; a tumbler includinga head adapted to bear against said plunger, a stem extending into and through said constriction and a tapered cam portion on said stem adapted as said stem is urged through said constriction to engage said camming element and move the extremityof the said stem remote from said head from a position oiset with respect to the axis of said housing to a substantially centeredposition; a hammer slidable in said housing on 'the opposite side of said constriction from said plunger; and a spring urging said hammer toward said restriction, tumbler and plunger; said hammer having an end adapted to be engaged by said stem when in its olset position and a socket in said end adapted to receive said stem when said stem vis in its aligned position, wherebyy on receiving'said stem the hammer is driven by said spring into impact engagement therewith.

2. A construction as set forth in claim 1 Wherein a'shoulder inclined relative to the axis of said stem is provided between said stem and its head and a spring is interposed between said shoulder and said constriction and urges said` stem into its inclined position.

LAURENCE A. SWEET. 

